Polymeric composites that contain organic and/or inorganic filler materials have become desirable for a variety of uses because of their excellent mechanical properties and weathering stability. Foamed versions of these materials can have a relatively low density yet the filler materials can provide a composite material that is extremely strong. The polymer provided in the composite can help provide good toughness (i.e., resistance to brittle fracture) and resistance to degradation from weathering to the composite when it is exposed to the environment. Thus, polymeric composites including organic and/or inorganic fillers can be used in a variety of applications.
The use of polyurethane composites has grown over the last three decades. This can be attributed to their superior tensile strength, impact resistance, and abrasion resistance compared to, for example, unsaturated polyester and vinyl ester-based composites. Typically, low density polyurethane composites are made by adding a gaseous phase in-situ to the polyurethane binder, for example, using water and isocyanate to produce carbon dioxide or by introducing blowing agents. However, a persistent problem in making low density composites with such methods includes compromised mechanical and physical properties of the composite. In particular, the flexural strength and handleability decrease sharply as the density of the composite decreases. There is a need to improve the properties of filled composites. The compositions and methods described herein address these and other needs.